package org.apache.lucene.document;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.zip.Deflater;
import java.util.zip.Inflater;
import java.util.zip.DataFormatException;
import java.io.ByteArrayOutputStream;
import org.apache.lucene.util.UnicodeUtil;

/** Simple utility class providing static methods to
 *  compress and decompress binary data for stored fields.
 *  This class uses java.util.zip.Deflater and Inflater
 *  classes to compress and decompress.
 */

public class CompressionTools {

    // Export only static methods
    private CompressionTools() {
    }

    /** Compresses the specified byte range using the
     *  specified compressionLevel (constants are defined in
     *  java.util.zip.Deflater). */
    public static byte[] compress(byte[] value, int offset, int length, int compressionLevel) {

        /* Create an expandable byte array to hold the compressed data.
         * You cannot use an array that's the same size as the orginal because
         * there is no guarantee that the compressed data will be smaller than
         * the uncompressed data. */
        ByteArrayOutputStream bos = new ByteArrayOutputStream(length);

        Deflater compressor = new Deflater();

        try {
            compressor.setLevel(compressionLevel);
            compressor.setInput(value, offset, length);
            compressor.finish();

            // Compress the data
            final byte[] buf = new byte[1024];
            while (!compressor.finished()) {
                int count = compressor.deflate(buf);
                bos.write(buf, 0, count);
            }
        } finally {
            compressor.end();
        }

        return bos.toByteArray();
    }

    /** Compresses the specified byte range, with default BEST_COMPRESSION level */
    public static byte[] compress(byte[] value, int offset, int length) {
        return compress(value, offset, length, Deflater.BEST_COMPRESSION);
    }

    /** Compresses all bytes in the array, with default BEST_COMPRESSION level */
    public static byte[] compress(byte[] value) {
        return compress(value, 0, value.length, Deflater.BEST_COMPRESSION);
    }

    /** Compresses the String value, with default BEST_COMPRESSION level */
    public static byte[] compressString(String value) {
        return compressString(value, Deflater.BEST_COMPRESSION);
    }

    /** Compresses the String value using the specified
     *  compressionLevel (constants are defined in
     *  java.util.zip.Deflater). */
    public static byte[] compressString(String value, int compressionLevel) {
        UnicodeUtil.UTF8Result result = new UnicodeUtil.UTF8Result();
        UnicodeUtil.UTF16toUTF8(value, 0, value.length(), result);
        return compress(result.result, 0, result.length, compressionLevel);
    }

    /** Decompress the byte array previously returned by
     *  compress */
    public static byte[] decompress(byte[] value) throws DataFormatException {
        // Create an expandable byte array to hold the decompressed data
        ByteArrayOutputStream bos = new ByteArrayOutputStream(value.length);

        Inflater decompressor = new Inflater();

        try {
            decompressor.setInput(value);

            // Decompress the data
            final byte[] buf = new byte[1024];
            while (!decompressor.finished()) {
                int count = decompressor.inflate(buf);
                bos.write(buf, 0, count);
            }
        } finally {
            decompressor.end();
        }

        return bos.toByteArray();
    }

    /** Decompress the byte array previously returned by
     *  compressString back into a String */
    public static String decompressString(byte[] value) throws DataFormatException {
        UnicodeUtil.UTF16Result result = new UnicodeUtil.UTF16Result();
        final byte[] bytes = decompress(value);
        UnicodeUtil.UTF8toUTF16(bytes, 0, bytes.length, result);
        return new String(result.result, 0, result.length);
    }
}
